Career Summary

Biography

Research ExpertiseStructure of turbulence, transport of momentum and heat in different shearflows Transport properties of the atmospheric surface layer, turbulent diffusion, properties of small-scale turbulence Manipulation of turbulence, management and control of turbulent flows.

Qualifications

PhD, University of Sydney

Master of Engineering Science, University of Sydney

Bachelor of Engineering, University of Sydney

Keywords

Mechanical Engineering

Fields of Research

Code

Description

Percentage

091399

Mechanical Engineering not elsewhere classified

50

020399

Classical Physics not elsewhere classified

15

091599

Interdisciplinary Engineering not elsewhere classified

35

Professional Experience

UON Appointment

Title

Organisation / Department

Awards

Recipient

Year

Award

2007

For contributions to turbulence research Australian Academy of Science

A numerical simulation based on the lattice Boltzmann method is carried out in the wake of a square cylinder with the view to investigating possible surrogates for the instantaneo... [more]

A numerical simulation based on the lattice Boltzmann method is carried out in the wake of a square cylinder with the view to investigating possible surrogates for the instantaneous turbulent kinetic energy dissipation rate, Ie{cyrillic, ukrainian}, as well as its mean value, \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }$\end{document}Ie{cyrillic, ukrainian}. Various surrogate approximations of Ie{cyrillic, ukrainian}, based on local isotropy (Ie{cyrillic, ukrainian}iso), local axisymmetry along the streamwise direction x (Ie{cyrillic, ukrainian}a, x) and the transverse direction y (Ie{cyrillic, ukrainian}a, y), local homogeneity (Ie{cyrillic,ukrainian}hom), and homogeneity in the transverse plane, (Ie{cyrillic,ukrainian}4x), are assessed. All the approximations are in agreement with \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }$\end{document}Ie{cyrillic,ukrainian}when the distance downstream of the obstacle is larger than about 40 diameters. Closer to the obstacle, the agreement remains reasonable only for \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }_{a,x}$\end{document}Ie{cyrillic, ukrainian}a,x, \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }{hom}$\end{document}?hom and \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }{4x}$\end{document}Ie{cyrillic, ukrainian}4x. The probability density functions (PDF) and joint PDFs of Ie{cyrillic, ukrainian} and its surrogates show that Ie{cyrillic, ukrainian}4x correlates best withIe{cyrillic, ukrainian}while ?iso and Ie{cyrillic, ukrainian}hom present the smallest correlation. The results indicate that Ie{cyrillic, ukrainian}4x is a very good surrogate for Ie{cyrillic, ukrainian}and can be used for correctly determining the behaviour of Ie{cyrillic, ukrainian}.

We investigate the effect of the hot wire resolution on measurements of the velocity derivative skewness in homogeneous isotropic turbulence. A single wire configuration (with dif... [more]

We investigate the effect of the hot wire resolution on measurements of the velocity derivative skewness in homogeneous isotropic turbulence. A single wire configuration (with different lengths and temporal sampling resolutions) is considered. Estimates of the attenuation, based on numerical data in box turbulence, are applied to experimental data taken in grid turbulence. It is found that the sampling resolution has a sizeable attenuation effect, while the length of the wire has a relatively minor impact. The corrected experimental values support the conclusion that the skewness is constantwith the Reynolds number, in agreement with Kolmogorov's 41 theory.

Decaying grid turbulence is considered at low Reynolds number (R Â¿~ 50) for different initial conditions. Three different grid geometries are used. Heat is injected via a mandoli... [more]

Decaying grid turbulence is considered at low Reynolds number (R Â¿~ 50) for different initial conditions. Three different grid geometries are used. Heat is injected via a mandoline at a distance of 1.5 M from the grid. The amount of heating is such that temperature may be treated as a passive scalar. A small contraction (1.36:1) is added at a distance of 11M downstream of the grid. The power-law exponents for the scalar variance are compared with those for the turbulent kinetic energy. These exponents depend on the grid geometry. For the isotropic dissipation rate (Chi;) iso, the power-law exponent agrees with that inferred from the temperature variance transport equation. Restricting the range of validity of the decay law affects the magnitudes of the origin and decay exponent. Secondorder temperature structure functions collapse when the normalization is based on the local temperature variance and the Corrsin microscale but the asymptotic form of this collapse depends on the initial conditions.

Direct Numerical Simulations of turbulent channel flow with square bars on the bottom wall are discussed have been carried out at different Reynolds numbers. The results tend to c... [more]

Direct Numerical Simulations of turbulent channel flow with square bars on the bottom wall are discussed have been carried out at different Reynolds numbers. The results tend to confirm the inappropriateness of the roughness function as an indication of the effect a particular roughness geometry exerts on the flow. Distributions of turbulent intensities support the improvement in global isotropy relative to a smooth-wall.

Motions that are responsible for the production and maintenance of the Reynolds shear stress in a turbulent boundary layer may be affected by the Reynolds number and the surface r... [more]

Motions that are responsible for the production and maintenance of the Reynolds shear stress in a turbulent boundary layer may be affected by the Reynolds number and the surface roughness. Evidence for each of these effects is presented, based mainly on experiments carried out in our laboratory. The effects are felt in both inner and outer regions of the layer. The evidence points to the non-universality of the active motion and to the sensitivity of the large scale motion to boundary conditions.

The small-scale structure of turbulence is studied by measuring the statistics associated with Â¿u/Â¿y in the turbulent wake behind a circular cylinder for a moderate range of RÂ¿... [more]

The small-scale structure of turbulence is studied by measuring the statistics associated with Â¿u/Â¿y in the turbulent wake behind a circular cylinder for a moderate range of RÂ¿ (60-250). The results indicate both similarities and differences between the statistics of Â¿u/Â¿y and those of Â¿u/Â¿x. The pdf of Â¿u/Â¿y, like that of Â¿u/Â¿x, has long exponential tails which are Reynolds number dependent. The flatness factor of Â¿u/Â¿y is larger than that of Â¿u/Â¿x, implying that Â¿u/Â¿y is more intermittent than Â¿u/Â¿x. The spectrum of (Â¿u/Â¿y)2 does not exhibit any inertial range power-law dependence, a behaviour which has previously been observed in the spectra of (Â¿u/Â¿x)2. In the inertial range, the autocorrelation of Â¿u/Â¿y displays a r-4/3 behaviour while the autocorrelation of (Â¿u/Â¿y)2 is similar to that of (Â¿u/Â¿x)2, both yielding the same value for the intermittency exponent Âµ.

Antonia RA, Browne LWB, Bisset DK, 'Effect of Reynolds number on the organized motion in a turbulent boundary layer', Proceedings of the International Centre for Heat and Mass Transfer, 488-506 (1988)

Measurements have been made in a zero pressure gradient turbulent boundary layer in an attempt to quantify the influence of Reynolds number on features of the motion, which is org... [more]

Measurements have been made in a zero pressure gradient turbulent boundary layer in an attempt to quantify the influence of Reynolds number on features of the motion, which is organised on a scale comparable to the thickness of the layer, in the plane of main shear. These features have been obtained with an array of eight X-probes aligned in a direction normal to the wall, each probe measuring velocity fluctuations u (streamwise direction) and v (normal to the wall). Information derived from the u and v data includes conventional space-time velocity correlations, instantaneous and conditional particle paths and spanwise vorticity contours. The effect of Reynolds number on the spatial extent of isocorrelation contours is more important for u than v. No significant dependence on Reynolds number is observed for conditional particle paths but contours of conditional spanwise vorticity extend to a larger normalised distance from the wall at small Reynolds number. Contributions of the organised motion to the Reynolds stresses tend to be more important as the Reynolds number decreases.

The similarity between velocity and temperature fields in the self-preserving region of a plane jet is examined by considering spatial contours of ensemble averages of quantities ... [more]

The similarity between velocity and temperature fields in the self-preserving region of a plane jet is examined by considering spatial contours of ensemble averages of quantities formed using velocity u and v and temperature theta fluctuations. These averages were conditioned on the occurrence of temperature fronts observed with the use of a spanwise rake of temperature sensors. Reasonable similarity exists between overall correlation coefficients for u and v and for v and theta . There is also similarity between contributions from the random motion to these coefficients but, in this case, the spatial distribution is quite different than when the coherent contribution is included. Contributions to the Reynolds shear stress, temperature variance and lateral heat flux from coherent and random motions are roughly equal. The random motion makes a significantly larger contribution to the Reynolds normal stresses than does the random motion.

Thermal wake measurements have been made behind single hot wires, both well away from and very close to a conducting wall. Comparison with theoretical distributions highlights the... [more]

Thermal wake measurements have been made behind single hot wires, both well away from and very close to a conducting wall. Comparison with theoretical distributions highlights the transition from a two to a three dimensional wake as the distance from the wire increases. In the absence of a suitable theory, the measurements in wall proximity were analysed using enthalpy balances. The results provide a firm demonstration of the significant heat transfer to the wall that accompanies wall proximity. An implication of the theory, that wall proximity can be correlated using the wire heat transfer rate, is shown to have some experimental support.

The three components of the average temperature dissipation have been measured using a pair of parallel cold wires, in an approximately self-preserving thermal layer. Mean squared... [more]

The three components of the average temperature dissipation have been measured using a pair of parallel cold wires, in an approximately self-preserving thermal layer. Mean squared values OVER BAR theta OVER BAR **2//,//y and OVER BAR theta OVER BAR **2//,//z of temperature derivatives in the directions normal to the flow were mainly obtained from the curvature of spatial temperature autocorrelations. The mean squared value OVER BAR theta OVER BAR **2//,//x of the temperature derivative in the flow direction was mainly inferred from the temporal derivative of temperature and Taylor's hypothesis after the latter was verified at a few locations in the flow. A measure of the accuracy of the dissipation measurements is provided by the negligible imbalance in the temperature variance budget measured in the outer flow region.

Measurements of the thermal wakes behind single hot-wires have been made in both the free-stream above a boundary layer and in the region adjacent to the surface where the measure... [more]

Measurements of the thermal wakes behind single hot-wires have been made in both the free-stream above a boundary layer and in the region adjacent to the surface where the measured mean velocity rises above that given by the sublayer equation. The former results show that enthalpy balances within the wake are accurate to within 20%. As the hot-wire is moved toward the wall the much larger reduction in the enthalpy flux indicates a significant heat transfer to the aluminium wall. The concomitant increase in the measured mean velocity appears to be a function of the wire heat transfer rate, at least when the direct effects of the wire diameter can be ignored.

Two-point correlations of temperature fluctuations confirm the existence, in the self-preserving region of a plane jet, of spanwise structures, occurring alternately on opposite s... [more]

Two-point correlations of temperature fluctuations confirm the existence, in the self-preserving region of a plane jet, of spanwise structures, occurring alternately on opposite sides of the centreline. Conditional averages of temperature fluctuations are computed using a selection procedure based on information obtained at several points in space. The averages are compared with those obtained when the selection is based on information at one point in space.

The technique of K. N. Rao, R. Narasimha and Badri Narayanan (1971) is tested by applying it to both Gaussian noise and turbulent velocity fluctuation signals. Measurements includ... [more]

The technique of K. N. Rao, R. Narasimha and Badri Narayanan (1971) is tested by applying it to both Gaussian noise and turbulent velocity fluctuation signals. Measurements include the dependences of the pulse frequency and intermittency factor on the magnitude of the threshold and the dependence of the maximum pulse frequency on the centre frequency of the filter. Important differences exist between white noise and turbulent signal distributions. These differences persist when the white noise spectrum is shaped in an attempt to simulate the spectrum of the turbulent velocity fluctuation. Refs.

The exact transport equation for the dissipation or destruction of temperature fluctuations in a steady, two-dimensional shear flow is briefly discussed from the point of view of ... [more]

The exact transport equation for the dissipation or destruction of temperature fluctuations in a steady, two-dimensional shear flow is briefly discussed from the point of view of the experimenter's ability to measure the important terms. The transport equation for only one component of the destruction, the mean-square streamwise temperature derivative, is considered in more detail. Measurements of several terms of this equation have been made in the self-preserving region of a turbulent plane jet.

Temperature fluctuations in a turbulent shear flow are modeled by a ramp-like signal on which relatively high frequency Gaussian fluctuations are superimposed. Both linear ramps w... [more]

Temperature fluctuations in a turbulent shear flow are modeled by a ramp-like signal on which relatively high frequency Gaussian fluctuations are superimposed. Both linear ramps with fixed height and length and exponential ramps of variable length are considered. Parameters which characterize the exponential ramps are obtained from experimental data in a heated jet. High order moments of temperature calculated with the use of the ramp model are in reasonable agreement with available experimental measurements. Copyright & 1976 American Institute of Physics.

Using DNS data in a turbulent channel flow, the paper examines the effect of the surface geometry on the vorticity and (passive) scalar gradient vectors at a relatively small Reyn... [more]

Using DNS data in a turbulent channel flow, the paper examines the effect of the surface geometry on the vorticity and (passive) scalar gradient vectors at a relatively small Reynolds number and for a molecular Prandtl number of 1. While a strong correlation between these two vector fields is expected close to the wall when the latter is smooth, significant changes occur when the surface is modified by roughness elements. Different shaped elements, placed orthogonally to the flow with a small streamwise spacing, are considered. The largest and smallest disturbances occur for triangular and square elements respectively whereas the disturbance from circular elements is intermediate to that of the previous two geometries. This result is reflected in nearly all the small-scale statistics that have been obtained, including correlations between components of the vorticity and scalar gradient vectors. Local isotropy near the wall is more closely approximated for the triangular elements.

Burattini P, Djenidi L, Antonia RA, 'Effect of a Passive Disturbance on the Heat Transport in the Near Field of a Round Jet', Proceedings 13th International Heat Transfer Conference, Sydney, Australia (2006) [E1]

Burattini P, Antonia RA, Rajagopalan SR, 'Effect of initial conditions on the far field of a round jet', Proceedings of the Fifteenth Australasian Fluid Mechanics Conference, University of Sydney (2004) [E1]

Rehab H, Djenidi L, Antonia RA, 'LDV and PLIF Measurements in a Turbulent Boundary Layer Over a Rough Wall', Proceedings of the Second Australian Conference on Laser Diagnostics in Fluid Mechanics and Combustion, Melbourne (1999) [E1]